text:
Why does the DC-10's horizontal stabilizer have such a pronounced dihedral?
If you look at this picture, you'll see that the horizontal stabilizer has a very pronounced dihedral in comparison to the wings. Could somebody explain in a simple way why? I understand that a dihedral wing makes an aircraft more stable on the roll axis, but why on the horizontal stabilizer, which produces a downforce?
This question is not just about the DC-10, because there are also other planes that are not trijets and have this feature, I just used the DC-10 as an example
See also this schematic:

Image excerpted from original, by Julien.scavini, used under CC BY-SA 3.0

Speculation: the weight of the third engine (and plumbing) combined with a source of thrust so far up and aft might require more stabilization. Dihedral is cheaper that adding more hardware for a damping system. The L1011 has relatively little dihedral but also seems to have a much larger vertical fin.

Just conjecture by it might have something to do with getting the HS out of the downshift downwash from the wings.

the stability provided by diedral is coming from wing, not from stabilizer (less load). Looking at the plane one reason might be avoiding the wake of the twin engines in high angles of attack (where the stabilizer is dimensioned), I do not know for sure but likely is the reason

I noticed at the airport today (with this question in mind) a bunch of 737s, a 787, and to a lesser extent A330s with a very pronounced dihedral too.

At the airport you're only seeing the dihedral at rest.  Once in the air, the stab will have air loads, and that will bend it downward somewhat.  Remember stabs fly upside down, generally pushing downward on the tail

In a general sense, there are multiple reasons for the horizontal stabilizer to have dihedral/anhedral.

To clear the tail from the downwash/propwash. A good example is the Cessna 425, which was developed from the Cessna 421. The 421 had a straight horizontal stabilizer. However, with the addition of dihedral, the tail is kept out of the propwash, improving ride quality. From a report citing Cessna engineers:

Cessna engineers say the dihedral improves Dutch roll qualities and moves a major portion of the tail out of the prop wash, thus providing a smoother ride.

The Dassault Falcon 50 had anhedral so as to clear the tail from the wing's downwash. Another good example of this is the F-4 Phantom. The prototypes had a straight tail. However, the anhedral tail was adopted so as to keep it clear of the disturbed air from the wing at high angles of attack while at the same time keeping it out of engine exhaust.
The anhedral in BAE Hawk is explained by the same reason. From The Hawk Story:

This model gave the first indications of high speed problems due to interference between the high intake and the low wing, and the
  position of the tail.
This resulted in the adoption of a low intake, ... .The rear fuselage was cambered downwards  to bring the tail down, and the tailplane was
  given pronounced anhedral for the same purpose.

Stability- The dihedral/anhedral in the stabilizers affects the aircraft's stability. In short, for a conventional tail, an anhedral improves the yaw stability of the aircraft while reducing the pitch stability (slightly), while a dihedral will reduce the tail's contribution to both pitch and yaw stability.
However, the use of dihedral in the horizontal tail influences static roll stability in the same way as that of dihedral in the wing. Dihedral affects the roll response in the same way as that of the wing- it causes the lift on the right and left semispans to respond differently to downwash.
A good example of this is the Vickers Viscount, which had a dihedral horizontal stabilizer, which improved its stability.
Due to this, it is better for the designer to add a dihedral to the horizontal tail rather than wing especially if problems are found in later stages of design as the impact will be lesser.

From Roskam's Aircraft Design Vol III, Chapter 5.1:

The overall lateral stability is usually dominated by the inherent lateral stability designed into the wing. Wing sweep, dihedral angle and (wing) location on the fuselage dominate the magnitude and the sign of the stability derivative. Since the wing is designed by performance and operational considerations, the empennage is often used to fine tune the lateral stability of the aircraft. Examples include the F-4 and the AV-8B.

It should be noted that, as with any other design consideration, the dihedral of the horizontal stabilizer depends on the design choices made and perfomance characteristics required; as a result, the configuration required will change from aircraft to aircraft.
In case of DC-10, the main reason appears to be to keep the stabiliser out of the wing influence, especially when high flap settings are used. The more pronounced dihedral (compared to, say Boeing 737) appears to be used as the stabilizer is mounted lower due to the presence of engine in the tail.

Now, when you say dihedral is that realtive to the lift produced? Since the horizontal "lifts" down is dihedral the correct term to describe what we see in the DC10 or is it actually anhedral?

@acpilot the terms dihedral and anhedral refers to the angle (of the wing/stabilizer) to the wing. So, if the stabilizer is at an angle so that the tip is above the root, it is dihedral. DC-10 has a dihedral in its stabilizer, while F-4 has anhedral.

I don't understand your answer. How can you measure the dihedral of a wing against itself? I think you are asserting that di/anhedral is measured realtive to the airframe "top" without regard to anything else and has nothing to do with which side of the surface is actually creating "lift," correct? For example, wings can be angled "up." To achieve the same effect on the horizontal you'd need to angle them "down." In this case, does the wing have dihedral and the horizontal have anhederal or, since both surfaces are angled in the direction of lift, do they both have dihedral?

@acpilot I'm not measuring the wing di/anhedral against itself. I'm measuring it against a horizontal plane passing through the wing/stabilizer root(s). Yes, it has nothing to do with which side is creating lift and is purely a function of geometry. If the stabilizer is angled down, it has anhedral, not dihedral.

Thanks.  I'd never thought of it in terms of lift and it's never come up in training.  Good to know!

Most airliners with low horizontal tail surfaces have dihedral on them, for two reasons:

To lift the horizontal surface above the wing wake.
To lift the swept tail above the ground, so it will not be damaged in a tail strike. Note that the tail is roughly horizontal at the tail strike attitude to have enough clearance for full down elevator deflection.

Boeing 747-400 tailstrike (picture source)

Given enough angle of attack, a swept, un-dihedraled tail surface will touch the ground with the tips first (picture source)
In a T-tail, both reasons don't exist, so T-tails are straight in most cases. A notable exception would be the Handley-Page Victor, where a noticeable dihedral was added late in the design process to increase the projected side area of the tail section. Thanks to @ymb1 for finding this article which includes a detailed description of the Victor.
Vertical area is always too small initially, just witness the tail growth in the BAC Lightning. Interestingly enough, the article says that the vertical on the Victor was shortened after flight test. This is an extremely rare occurrence.

Handley-Page Victor (picture source)

The horizontal tail has pronounced dihedral in almost all low tailplane placements. Two major factors are:

Lifting the tail plane out of the jet efflux area. Placement of the stabiliser root is structurally optimal when at fuselage mid, dihedral can then lift the surface out of the efflux stream. If the fuselage aft cone is lifted up already there is less requirement for tailplane dihedral.
Reducing sudden main wing wake effects: with a pronounced dihedral, there is always some of the tailplane sticking out into a less affected streamline.

Note that a stabilising roll moment from tail plane dihedral would have to be transferred through the fuselage: the torque difference between main wing and tail wants to twist the fuselage like a wet rag. Not super consequential for structural loads, but the yield may cause difficulties with the flight control cable run. Wide body aircraft are least affected by this.


text:
What is the difference between a stall fence and a vortex generator?
Both of them prevent the aircraft from stalling, so is there any difference between them? The wing fence doesn't produce a vortex, so how does it work?

Several wing modifications

A fence will create a vortex, just like a vortex generator, due to crossflow near the leading edge. All those devices (dogtooth, notch, fence, vortex generator) are working in the same way. Their difference is the shape.

"prevent the aircraft from stalling"  More like: reduces the airspeed at which the wing stalls (ex. 50 knots to 45 knots), or increases the AOA at which the wing stalls, or improves the handling of the aircraft at slow speeds.

The wing fence is more or less what it is called- a fence. For swept wing aircraft, the local flow is not along the direction of flight, as there is a significant spanwise flow from the center towards the tips. It can be seen in the following figure.

Image from fuckyeahfluiddynamics.tumblr.com
The end result is that the boundary layer continues to grow (thicken) in this direction, with outboard regions more prone to stall than inboard ones. Basically, the wing fences stop the spanwise flow, with the result being a new (thinner) boundary layer starts on the other side of the fence.
In case of a vortex generator, the VGs basically create a vortex which re-invigorates the boundary layer by mixing free stream air with that of the boundary layer, thereby preventing separation.

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text:
What kinds of materials are used for fighter jets' glass windshields?
What kinds of materials are used for fighter jets' windshield glass, and are they different from what they use for commercial jets?

By "glass shield", do you mean the "glass" used for the cockpit windows / canopy?

Related and amusing: AEDC Chicken Gun.

@reirab "a dead chicken prepared in accordance with the ASTM specification." Would love to meet the people who wrote that spec.

@egid Since it also says the people at the range "played an instrumental role in developing the ASTM F330 specification," I probably met some of them at one point or another. haha I worked at AEDC for a while.

@egid Also, I'm sure that specification sounds a lot more interesting than it really is...

Today, the canopy is a multi-layer structure. In case of the F-16, it consists of three layers:

The innermost layer is 0.5 inch thick polycarbonate and drape-molded into the compound curvature shape.
The center layer is 0.05 inch polyurethane to bond the inner to the outer layer.
The outer layer is a 0.125 inch layer of acrylic (PMMA).

The canopy is bolted to a metal frame for assembly. Some canopies also use explosive cord on the outer layer to fracture the material shortly before the ejection seat fires.

F-16 canopy (picture source)
For less fast aircraft, a single layer of acrylic is sufficient. Funnily, the company which produces most of those canopies doesn't even have a page in Wikipedia. They use flat PMMA sheets and drape-mold them over a mandrel. The secret of their process is the grease they put on the mandrel so the acrylic flows easily into shape.

Can you talk a bit about why 3 layers are needed and what they all do?

@DavidGrinberg - One possible concern: Ballistic resistance of double-layered armor plates: "In a previous study of the same authors, it was shown that a double-layered shield of the same metal was able to improve the ballistic limit by 7.0–25.0% under impact by a flat-nose projectile, compared to a monolithic plate of the same weight." I did this experiment in HS ;)

@mins They still are not mentioned in Wikipedia. My answer linked to the company site already.

The fighter jet canopies usually are made of (special) acrylic plastics or polycarbonate, with special coatings for RCS reduction in some cases.
In general, different fighter canopies differ in their material and construction.
The F-22 canopy is the largest piece of monolithic polycarbonate material being formed today. It has no canopy bow (frame) which helps in having superior optics throughout the canopy (not just in the front) and also offers the requisite low-observable features.

Source: www.abovetopsecret.com
The canopy is 3/4" thick and is actually made of two 3/8" thick sheets that are heated and fusion bonded (the sheets actually meld to become a single-piece article) and then drape forged.
On the other hand, F-16's canopy, is made up of laminated polycarbonate-acrylic canopy.

Source: designer.home.xs4all.nl
In general, a laminated canopy offers better birdstrike protection; however, lamination also adds weight as well as reduced optics. Some aircraft have gold tinted canopies like the EA6B Prowler.

"EA-6B Prowler takes off from Eielson AFB" by Camera Operator: SSGT CHERIE A. THURLBY, USAF - ID: DFSD0405331 / 020423F7203T025]. Licensed under Public Domain via Commons.
The gold tinting performs two different functions:

On an EA-6B it serves to protect the crew from the radiation emitted by their own jamming pods (EA6B can carry upto 5 jamming pods).
On other aircraft like F-16 and F-22, it prevents radiation (from Radar) from reflecting off the interior cockpit structure, reducing RCS.

Commercial jets use Plexiglas or Poly(methyl methacrylate) (PMMA) in their windows.
Sources: PPGaerospace, globalsecurity.org

That Prowler is from my old squadron, and I was at Eielson for Northern Edge in 2002!  Unfortunately a death in the family took me out of the flying rotation, or else I could claim "that mighta' been me..."  But I undoubtedly knew the crew.

Thank you for your service, @MichaelHall! My son is currently just down the road at Wainwright.

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text:
What kind of Gyros are being used in smaller regional jets?
As per my understanding, most of the Gyros in big jets are electric driven but I am not sure if the smaller planes also have the electric driven or vacuum/pressure driven Gyros?

These days aircraft use solid state gyroscopes or occasionally laser gyroscopes. They are cheaper and more reliable. The downside is that they only work as rate gyros, so a computer is needed to integrate the orientation, but that has advantage that it does not have problems with tumbling (though depending on how the calculation is done, some may still loose precision near vertical).

@Jan Hudec, you should put that as an answer. Related answer

@DeltaLima: Real answer should say whether bleed air is or was used to drive gyros, somewhere, which I don't know.

The question is not too precise. Are you asking if vacuum gyros exist, or maybe are, or even have been equipped in an aircraft? Answer to all of those would be yes. Smaller planes? Smaller than commercial jets, regional turboprops, 20-seaters, 2 seaters?

now why did this question make me think of https://en.wikipedia.org/wiki/Gyro_%28food%29 :) Maybe I shouldn't read this site while hungry...

Yes small planes have electric gyros as well. It can be as sophisticated as Garmin 1000 in Cessna 172 or Russian made electric artificial horizon gyro powered by accumulator in a glider Blanik L13. I heard battery didn't last very long though:) Also all turn rate indicators have gyros and the ones I saw were electric powered. This ensures that you can still survive if a vacuum pump fails. Turn indicators used in the eastern block made gliders are powered by simple 4.5V battery.

Many planes are being/have been retrofitted with glass panels that use attitude heading reference system (AHRS) in place of vacuum driven gyros, with 4-hour or more battery backup in case the plane's electric system goes down. Examples are the Garmin 1000 as mentioned, to something smaller like a pair of G5s or a G500.
https://buy.garmin.com/en-US/US/p/pn/K10-00280-00
https://buy.garmin.com/en-US/US/p/pn/TXi-0G500-03
https://buy.garmin.com/en-US/US/p/pn/010-G1000-00


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What modifications would be required to use a DHC-6-400 for Carrier Onboard Delivery work?
In the spirit of our small airplane landing on a carrier question, I decided to up the ante slightly in a couple of ways.
Let us say some enterprising foreign navy has found a small flattop under their Christmas tree this year, and is in need of some aircraft to fly off it.  Of course, tactical aircraft are a necessity, and to that end, they could obtain some used A-4s as a starting point for their fledgling naval aviation branch.  However, there are other important aircraft on a carrier deck, one of them being the Carrier Onboard Delivery plane.  A bright young naval officer there decides "Hey, we should see if some small civil planes might work for what we need", and does a bit of research, stumbling upon the DHC-6-400 with its widespread support base, ease of maintenance, good STOL performance, and current production availability.
How much modification would our enterprising foreign navy need to ask Viking Air to do to their order of DHC-6-400s to be fully usable from a carrier deck?

Interesting question and well written.

Given that most carriers can generate at least 35kts of wind over the deck, your takeoff and landing distance would be damn near zero... deck size is NOT a constraint here.  A twin otter can touch down at 50-60kts indicated, and can basically stop on a dime even in zero-wind conditions.

DHC-6 has a reported takeoff roll of 210m and landing distance of 155m and as such can be operated from most of the aircraft carriers in service, albeit with limited capability. If required, the aircraft can takeoff into the wind and for arrested recovery rear fuselage can be strengthened, though this looks unnecessary.
It may need some changes for operating in marine environment like,

better corrosion protection
strengthened landing gear
Required naval equipment (for TO/landing).

Of course, all these modifications will eat into the payload. DHC-6 would be a rather small COD aircraft. The C-2 Greyhound used in USN has a payload greater than the MTOW of the twin otter.

Indeed it would be -- that's why I suggested it for a small flattop :)

A great many Otters are already in service as seaplanes, and I understood that the -400 series is built with corrosion protection already sprayed on.

Or indeed, scheduled landings on a beach at low tide (EGPR)

The 25–30 knot headwind that a carrier is always able to get will also help significantly with the landing distance, especially when it is almost half of the landing speed.

Twin Otters have been used as seaplanes for decades. that's not the problem.


text:
Why did Britain develop three different bombers (V-bombers) after WW2 instead of one?
Why did Great Britain develop three different planes - Victor, Valiant and Vulcan - after WW2 for the same task?
I suppose that at that time the US and the Soviet Union were producing high numbers of bombers too, but did those countries stick to one design? Why did France not produce different bombers? My main question is about the effort of Great Britain and I am listing other countries only as examples.
Here is the Handley Page Victor:
(source)
Here is the Vickers Valiant:
(source)
and the Avro Vulcan:
(source)

It was the Victor, not Vickers. Vickers was an aircraft & tank manufacturer.

We designed the first two, decided we needed 100% more awesome so along came the Vulcan.

All modern aircraft have four dimensions: span, length, height and politics.

It was actually 4! The Short SA4 Sperrin was conceived as the safe fallback position whilst the other three underwent design and development. https://en.wikipedia.org/wiki/Short_Sperrin

@squigbobble - ...and Vickers made the Valiant but not the Victor nor the Vulcan. :-)

I've heard numerous reasons cited - perhaps due to the secrecy around all things nuclear - but from what I know, there are a few reasons:
Speed of deployment
Of the three designs, the Valiant was simplest, and could therefore be built and deployed the soonest. The initial Valiant prototype didn't actually meet the requirements that had been set forth for a nuclear-capable bomber aircraft, but it was better than nothing and with the mounting threat that the Cold War might turn hot, this speed was an asset, so the requirements were changed to allow the Valiant to enter service. This would fill the gap in the UK's forces, and more advanced aircraft could follow later.
Specialisation
Each of the V-bombers had slightly different performance, meaning that they could perform slightly different roles.

The Victor had the greatest payload capacity (up to 35 thousand-pound bombs)
The Vulcan was smaller and more agile and could therefore use smaller runways, and could just about break Mach 1 in a slight dive. It could also be refuelled in flight.
The Valiant was the simplest design, and therefore the most reliable (although it later emerged that a newly-developed and poorly-understood alloy introduced some serious design flaws)

Spreading the risk
Overall, the differences between the various aircraft were pretty minor, and the main reason that three contracts were allowed to progress to delivery was simple: the UK didn't want to put all their eggs in one aeroplane. The need for a nuclear deterrent - and a means to deliver it - was so great that it could not be jeopardised by a poorly-designed bomber, a mismanaged project, unforeseen failure of the company building the aircraft, etc. By having three aircraft from three different manufacturers, the UK greatly improved their chances of having at least one aircraft that actually worked, was delivered on time, and was able to remain in service for a reasonable period of time.

To quote John Hurt's character from Contact: "First rule in government spending: why build one when you can have two at twice the price?"

Note that multi-manufacturer overlapping procurement for risk mitigation worked quite well during WW2: http://www.wwiiequipment.com/index.php?option=com_content&view=article&id=116:british-production-of-aircraft-by-year-during-the-second-world-war&catid=48:production-statistics&Itemid=61

After the end of WWII there was an awareness at the British air ministry that a new type of bomber would be needed for nuclear warfare against the USSR. The specification that the government put forward required radical designs and the government was concerned they might fail, so they decided to go forward with 3 of them to ensure they had a nuclear deterrent in place.
There was also likely politics involved. At the time Britain was one of the leaders of aviation design and production, it was one of the few things going right in Britain at the time. The government felt it was important to support that industry, even though it meant higher costs.

authors: Bob Jarvis - Слава Україні

authors: Ильдар Усманов


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What is the work routine of a boomer operator in a refueling aircraft?
This is a boomer operator:

(source by John E. Lasky - United States Air Force)
If he is not refueling an aircraft, or the plane is not on a refueling mission, what is he doing? Is he sitting in that small cabin all the time, or is he free to move on the aircraft? Can his role be taken by anybody from the crew, or is he the only person on board who can handle the refueling boom?

You actually have to "fly" the refueling boom which requires special training so I'm pretty sure that not just anybody can operate the boom.

Just to make that clear: the control surfaces you see on the end of the boom there, are actual working aerodynamic control surfaces. The boom is not rigidly attached to the aircraft and steered by lever force, it is truly "flying" behind the tanker, and the boom operator has to fly it like towed glider, with the added difficulty of flying backwards.

@JörgWMittag The lateral control is reversed though, so the operator moves the stick left to move it left, he doesn't have to think "in reverse".

The boom operator (or boomer) can freely move around the aircraft. The boom operator position is usually accessible from the cargo hold and the operator can use the opening to move from his/her position. This is especially important for the KC-135 Stratotanker, which has the boom operator working in a prone position.

Image from sobchak.files.wordpress.com
While the operator is not fueling other aircraft, he/she has other responsibilities to carry out. According to the US military job description of a boom operator, the boomer,

Prepares and verifies load plans, directs cargo loading, and unloading operations, and inspects aircraft load to ensure hazardous cargo compliance and weight and balance status of aircraft. Ensures adequate safety equipment and passenger comfort items are on aboard aircraft. Instructs passengers in use of emergency equipment and emergency procedures.

among other things.
The boom operator is a specialist and his/her job cannot be done by anyone else on board. The operator also has to be qualified for the type of aircraft he/she is refueling. From interview of a USAF boom operator in foxtrotalpha:

Every receiver is a little different, so we have specific qualifications for heavy aircraft and fighter aircraft, called gulf and Charlie.

I think it should be Golf and Charlie, but I can't find any other sources that refer to that.

"Golf" is the correct ICAO/NATO phonetic alphabet word for G, but if you say "Gulf" when the listener is expecting an ICAO letter word, he'll hear "Golf".

As far as the answer, it's excellent, but I would add that these tankers usually have pretty full fueling schedules during their flight, so while a tanker is in the air the boom operator is usually in his cubby, as he doesn't have much time to be anywhere else.

How long does it take the tanker to get on station, or to leave station? Presumably the boomer has nothing to do during that time, and should nap or read a book...

@Roger Lipscombe That sounds like a nice job :-)


text:
What accidents have had crew accustomization to warnings among their causes?
A non-answer on this question claimed that:

the idea that maneuvering with the stall warning activated will somehow damage us, causing us to ignore its warning when the chips are down and AOA is up, is just silly

which sounds wrong to me, as I vaguely remember reading about crews becoming accustomed to frequent warnings, spurious or real, and disregarding them when they became critical.
Which, if any, aviation accidents or incidents have had among their direct or contributing causes a crew that ignored a warning due to being used to it being spurious or unimportant?
I am looking for substantiated answers only, remember that this site is not a venue to speculate on aviation accidents.

I recall an episode of aircrash investigations where the crew pulled the fuse on a nuisance warning during taxi, which then had consequences during flight. Though I don't quite recall which flight that was and my google-fu is failing me on it.

@ratchetfreak I think I've read that report, but can't recall the details; I'll give it a try.

The pilots on LAPA 3142 ignored the configuration warning, but I don't remember why.

@TomMcW afaik, due to an ongoing personal discussion. The report is quite dry and does not provide details, but there doesn't seem to be any indication of them being used to it.

Gradual accustomisation to abnormal situations which causes an incident is called 'normalisation of the deviance'. There is a very nice write-up by Tim Davies, a former RAF instructor, where he explains it very well. It is not about warnings in this case, but nevertheless a good read.

Just last year the crash of an Air Niugini flight was directly related to pilots ignoring warnings

The captain and first officer ignored a total of 17 audible warnings that they were flying too low.
“The crew seemed to have disregarded and talked over all the caution
  annunciations. The crew had experienced those type of cautions on
  previous flights and perceived them as nuisance alerts with no
  resultant consequence.”

I decided to give this answer the tick because it is, in my opinion, the most clear-cut example of accustomization from among the answers provided.

A Valan Air Cargo An-26 crashed in Cote de Ivoire on the 14th of October, 2017, while performing a charter flight. The aircraft descended below minimums on approach and impacted terrain, in this case a water body, short of the runway.
Among the contributing factors, the BEA listed "De-activation of EGPWS audible warnings due to nuisance alerts".
The following is taken from the translation of the  report provided by AVHerald, so I cannot confirm its accuracy; the original report can be found here if any French speakers want to double check. Emphasis mine:

The BEA reported the EGPWS was found fully and properly working, however, even on the previous flights the EGPWS had been sounding premature terrain warnings obviously related to an incorrect altitude reported by the Air Data Computer. A difference of about 700 feet between altitudes reported by ADC and radio altimeter was recorded. While the GPS data appeared correct and agree with the radio altimeter, the ADC data transmitted via ARINC 204 bus appeared incorrect.
The BEA annotated: "The regular presence of untimely (premature) Alerts from the EGPWS may have encouraged the crew to ignore these alerts, probably going so far as to disable them."

Also:

The EGPWS nuisance alerts were confirmed to have been present for a number of flights, however, had never been reported to the company. Therefore no action to identify and correct the malfunction were undertaken. A reliable Terrain Warning would certainly have made the crew aware of the vertical profile and correct their flight path to climb.

I don't think that "deactivation due to nuisance alerts" should count. There were plenty of such cases, but this is something almost opposite: disable the warning so that you don't get accustomed to it. (A particularly nasty example when the crew disabled the gear together with the warning).

PA-44 has a gear warning whenever you pull throttles back; as a result, you may be descending for qute some time hearing these beeps. There is a mute button, but the instructor never used it when I flew the airplane, exactly so that we don't forget. But instead, I did feel that I just started to ignore it...

@Zeus I partially agree, except for two points: first, that the alerts were an ongoing issue during previous flights and went unreported, normalizing the entire situation, and second, that it is unclear to me from the AVHerald translation whether it was conclusively established that the alert was muted: "The regular presence of untimely (premature) Alerts from the EGPWS may have encouraged the crew to ignore these alerts, probably going so far as to disable them". I'll ask in the Hangar whether a French speaker could go through the report.

A notable accident was the Helios Airways Flight 522 crash, where the pressurization system was turned off and the pilots ignored the warning horn because they thought it was the takeoff config warning. From the Wikipedia page:

As the aircraft climbed, the pressure inside the cabin gradually decreased. As it passed through an altitude of 12,040 feet (3,670 m), the cabin altitude warning horn sounded. The warning should have prompted the crew to stop climbing, but it was misidentified by the crew as a take-off configuration warning, which signals that the aircraft is not ready for take-off, and can only sound on the ground.

The official accident report explains the source of the confusion in more detail (emphasis mine):

The Board examined the flight crew’s actions to disengage the autopilot and auto-throttle,
  and to retard the throttles upon onset of the warning horn. Given that the expected
  reaction to a cabin altitude warning horn would have been to stop the climb (there was no
  evidence to this effect), the Board considered such actions to signify that the flight crew
  reacted to the warning horn as if it had been a Takeoff Configuration Warning (the two
  failures use the same warning horn sound). [...]
The warning horn was designed to signal two distinctly different situations. The Board
  considered the role of experience in interpreting and reacting to the warning horn. In the
  course of his career, a pilot is generally likely to only hear the warning horn when it is
  associated with a takeoff and a takeoff configuration problem. [...]
Most pilots are not very likely to experience a cabin pressurization problem and the
  associated warning horn at any time during their line flying.

Conclusion: Never use the same warning for multiple situations, if the pilots will only get used to one of them, otherwiese they will ignore the warning for the other situtations!

This isn't the same thing as the OP is asking. It wasn't a case of becoming accustomed to an alarm, it was misidentification of the alarm.

@TomMcW Yes, but they misidentified it because they became accustomed to it.

@TomMcW I thought the same when I read the first draft, but with the extra information about the two alarms using the same horn, I think it does count.

On May 9th, 2012, a Sukhoi Sukhoi Superjet 100-95 on a demonstration flight in Indonesia crashed into a mountain while in clouds. The Terrain Awareness and Warning System (TAWS) gave warnings, and the crew could have still avoided the terrain up to 24 seconds after the first warning, but they ignored and then inhibited the warnings, commenting that it must be a database issue. The crew had believed in their brief that there was no high terrain nearby and then became disoriented.
On April 10th, 2010, a Polish Air Force Tu-154 crashed during landing. As they were landing at a military field, it was not in the TAWS database. This meant that the system did not recognize that they were trying to land and started giving alerts. Rather than using proper procedure and engaging the "terrain inhibit" function, the crew changed the captain's altimeter setting, telling the system it was higher than it actually was. They later ignored multiple TAWS warnings and did not follow proper go-around procedures until it was too late.


text:
Why does afterburner exhaust have "pulses"?
Instead of being consistently-dense, the afterburner exhaust looks "pulsed" in these pictures below.  Is this a trick of the camera, a natural result of interaction with the air, or is there some design science in the propulsion system that causes this effect?

You can see this awesome effect more closely here https://www.youtube.com/watch?v=swoCdEwbFRc

Those are known as "Mach diamonds" or "Shock diamonds" (and a number of other names) and are not a characteristic of the afterburner per se but are formed by standing waves in the exhaust when the pressure of the expanded exhaust gases do not exactly match external ambient pressure. They can be formed by either over-expansion or under-expansion of the exhaust gases. The diamonds form at the transition from sonic to supersonic flow which occurs immediately on the "downstream" side of a rocket or jet engine nozzle.
Photo from the link below:
SR-71 Blackbird taking off.

In rockets, flow through such a nozzle is always sonic at the throat (in all except trivially low pressure systems where it can be subsonic - but these are not usually encountered in practice.)
The following text assumes fixed engine and nozzle geometery.
In practice gas flow paths often use "variable geometery" designs to allow optimisation across a range of flow regimes. See "Varible Geometery systems" at the end for a discussion of this.
In jet engines, whether flow is sonic or supersonic at the exhaust depends on the design which in turn tends to depend on the application. "Pure jet" engines which use a combustion driven compressor to compress input air and which develop their thrust from the jet exhaust will usually have supersonic exhausts. Ongoing development has led to a range of "jet" engine types with somewhat differing capabilities - turbojet ("pure" jet), turbofan (jet driven internal "fan" produces air which partially bypasses jet proper), turboprop (jet drives external propeller),propfan (turboprop on steroids optimised for close to Mach 1 cruise) and some fellow travelers such as turboshaft - like a turboprop but with shaft output - useful if you want to power eg a helicopter.
In a turbo-fan engine the amount of air which bypasses the jet engine proper is governed by the "bypass ratio". High bypass engines send most air past the jet proper to be combined with the jet exhaust and form the actual engine exhaust. Pure jet or some "low bypass ratio" turbo fan engines may have supersonic exhausts while "high bypass ratio" turbofan are always subsonic. Modern long distance aircraft (especially airliners) which aim for maximum fuel economy tend to have high bypass ratios. As Mach diamonds are only associated with trans-sonic operation you will not see Mach diamonds from eg a 747.
So, low bypass fanjets may have supersonic exhausts for part of their operation. A turbojet may be sub or super sonic and afterburner will almost always (but not necessarily in theory) produce supersonic outlet flow.
In systems which do have supersonic exit exhaust velocities, as the flow changes from sonic at the nozzle throat to supersonic in the expansion system the aim is to make the exit pressure exactly match ambient. "Exactly" never exactly happens in practice. Where the mismatch occurs there will be a shockwave - an "impedance mismatch in another perspective - and the visible evidence of this are the Mach Diamonds.
As both exhaust pressure and ambient pressure change with conditions there will essentially always be some degree of such shock waves present in "qualifying" systems, but more so when the engine operation departs more significantly from the ideal. Smaller versions may not be obvious without careful examination. As the overall system is usually optimised for "normal" conditions, afterburner operation is more likely to cause a major pressure mismatch as it deviates from normal use.
An exception would occur if the designers decided they wanted absolutely maximum performance from afterburner under given conditions (so that eg an interceptor could achieve absolute maximum velocity when needed) - in which case the Mach diamonds could be minimised on afterburner and would be more pronounced in normal operation.

See this page for some good photos and the diagrams below -

Aviation Aerospace - Shock Diamonds and Mach Disks

Below: creation of Mach Diamonds from under-expanded flow.

Below: - creation of Mach Diamonds from over-expanded flow.

Good explanation with pictures here - Wikipedia - Shock Diamond
Numerous relevant images - each linked to a related web page.

Variable Geometery systems:
Wikipedia Propelling nozzles

A propelling nozzle ... converts the internal energy of a working gas into propulsive force; it ... forms a jet, that separates a gas turbine, or gas generator, from a jet engine.

Propelling nozzles may have a fixed geometry, or ... variable geometery to give different exit areas to control the operation of the engine when equipped with an afterburner or a reheat system.
When afterburning engines are equipped with a convergent-divergent nozzle the throat area is variable.
Nozzles for supersonic flight speeds, at which high nozzle pressure ratios are generated, also have variable area divergent sections.
Turbofan engines may have an additional and separate propelling nozzle which further accelerates the bypass air.

Propelling nozzles also act as downstream restrictors, the consequences of which constitute an important aspect of engine design.

Characteristics of flow and thrust variations in a jet engine with a variable area nozzle
Paywalled, but freely accessible abstract is useful.
Automotive - but relevant Variable-geometry turbocharger (and interesting :-) ).
Useful Google search on variable geometery jet engine which provides a wide range of pages discussing these features.
AND an even more useful image search using the same terms - each image links to a related page.

Related:
Wikipedia - Jet Engine excellent.
He178 0- the very first Jet aircraft
NASA visual Turbojet simulation

@fooot  Indeed. Thanks. Twas true. I'd noted the omission and was going to address it but was re-re-re-editing and expanding the rest as well. I've now made the point that at the throat (especially evident in a pure rocket system) the velocity is (exactly) sonic (for the local conditions). This isolates conditions upstream from the effects of the downstream 'impedance bump', but getting into that in an answer like this is liable to produce glazed eyes :-).

I hope there is a place for "layman's terms" as well as more technical explanation here. We do have some pretty complicated answers on certain questions.

Combining your answer and Peter's into even more layman's terms: A boundary layer is formed between the atmosphere and the exhaust and the exhaust bounces off this boundary layer for a while. The fact that there are glowing combustion particles in the exhaust allows us to see the these bounces and they form nice little diamond shapes. Correct?

This effect needs

supersonic exhaust speeds and
high ambient density

to occur. Normal jets have subsonic exhaust speeds, and only the convergent-divergent nozzle of afterburning engines can produce the supersonic speed required. Inside the nozzle the air is accelerated by converting pressure into speed in a diffusor, the last part where cross section increases downstream.
Remember that supersonic gas has no means of being influenced by what happens downstream. In the nozzle it is easy to accelerate the exhaust gas so much that its pressure drops below 1 bar - just make the end cross section of the diffusor wide enough. When this low-pressure, supersonic jet leaves the nozzle and is confronted with ambient air, the air pressure will compact the jet. This can be seen very well in Russel's lower picture: A shock will form from the circumference of the nozzle and produce a cone which separates the low-pressure core of the exhaust gasses from the downstream section which is affected by air pressure.
Now something interesting happens: When the shock waves meet in the middle, they get reflected outwards, and what follows is a sequence of inward- and outward-traveling shocks which form this distinct diamond pattern. That it is visible at all is due to the carbon atoms in the fuel which glow orange because of their heat. The compression shocks originating from the circumference of the nozzle are  reflected at the center, turning into expansion fans when reflected at the boundary of the hot exhaust gasses and ambient air, and become compression shocks again when reflected at the boundary the next time. The compression will heat the flow, igniting remaining fuel and thus intensifying the glow of the carbon atoms, and the expansion will cool it, so you see alternating patterns of bright and dark, separated by the oblique shocks.

The same happens with rockets at lower, high-density altitudes. Rocket designers have to find a compromise between small, lightweight nozzles which have a high exit pressure (and waste some of the energy in the rocket fuel by not accelerating the exhaust gasses as much as possible) and bigger nozzles which also have lower exit pressure than 1 bar and have better efficiency at higher altitude. If the nozzle is optimized for higher altitude and over-expands the exhaust gasses when operated closer to the ground, the same shockwaves become visible. The picture above is from Copenhagen suborbitals.

do the shock diamonds still occur invisibly without the afterburner?

@raptortech97: Without the AB the exit speed is subsonic - only re-heating will accelerate the flow to supersonic speed. But if you use hydrogen as fuel (rockets!), the diamonds occur in the same way but are almost invisible - just a faint blue glow can be seen.

@PeterKämpf My understanding is that whether the speed is supersonic without after burner depends on the engine design. Straight turbojets can easily be designed with supersonic exhaust velocity and some low bypass turbofans at some parts of their operating range. I'm happy to hear comments on this and/or be told of references which may improve my understanding.

@RussellMcMahon: You're right, supersonic flow does not require afterburners. The combination is uncommon, though. It was more prevalent in the early jet age. Also, only the afterburner will add enough unburnt fuel to the exhaust gas such that shock diamonds become visible.

I have one little question. In this picture, it shows a jet engine at full afterburner. The thing is, the shock diamonds look like just rings or ‘donuts’ going around the circumference of the exhaust. Why is the fuel reigniting just around the outside of the exhaust? I can find a better picture when I’m able.

(I did double check that I wasn’t asking something already stated in your answer, but if what I’m asking doesn’t make sense I will happily clarify!)

@Wyatt I have to guess, but the jet looks like it has almost atmospheric pressure and the rings are the consequence of density changes resulting from oscillations ("afterburner rumble") in the afterburner pipe. So they are not actually shock diamonds. See here for more: https://conference.isabe.org/content/scnotes/bobby/gtc15.pdf

That's interesting, not what I expected. I studied your answer a bit more and noticed something. In This picture, you can see (circled) where the atmosphere first starts to compress the jet. If you look closely, it seems like at first the jet isn't being 'squished' as much, and as the jet extends it starts to compress more. In other words, in the circled area you can see a cone shape, and that cone isn't an exact or perfect cone, but the sides are curved slightly. Why is this the case? (it could also just be an illusion) Thanks a ton for all of your help.

@Wyatt I agree, the cone right at the nozzle is a bit curved. This could be from the drop in the speed of sound in the jet as it cools after exiting the nozzle. Just guessing, but sounds plausible to me. Inside the nozzle most IR radiation was reflected back into the jet. As it exits into the free air, IR is radiated away and the jet cools down. Slowly, of course.

That's a good point I didn't consider (that makes sense). Back to the rings in the jet exhaust, I ended up asking a question here. I thought I would add this so future readers could follow that link for an answer. (The question is more about why the outside of the rings are brighter than the center)

Sorry to ask another question in this already-long comments section, but otherwise it would require a whole separate question: In this familiar picture, I have outlined 2 areas in green. My question is why aren't these areas also getting compressed like the defined cone area right after the nozzle? It almost seems as though the outlined areas are atmospheric pressure and therefore not getting compressed like the cone area. I have been thinking about this for quite some time, and I can't quite figure out why.


text:
Were there any successful flying machines that did not rely on Bernoulli's Principle?
One of Leonardo da Vinci's flying machines appears to be a giant auger.  This design would not have exploited Bernoulli's Principle, but rather used the blade's rotation to push the air below it down to keep the craft airborne.

Image credit: Wikimedia
Were there any flying machines built like this that actually got off the ground?

EDIT: So maybe I have Bernoulli misunderstood, judging from the discussion.

paper airplanes

@Tyler - Paper airplanes are still technically Bernoulli. Just at a very small scale.

@Shawn No, there is no pressure differential on a flat wing. Of course, a paper airplane has no lift, but I would still classify it as a flying machine of a type. Another answer would be a kite.

But a paper airplane's wings aren't completely flat. It's just very minuscule. Or it's curved, which still exhibits Bernoulli's. So does a kite. Or a boat sail.  The first two have an excess of "thrust", but they'll still glide. And the first 2 can demonstrate lift and stalls if thrown lightly or gliding. No different than a curved wing. There's still a pressure differential. I think a sail can demonstrate those too, but I'm not a sailor, so not as familiar.

@Shawn I don't think this has anything to do with curvature. There are planes with completely flat wings (model airplanes) that can fly. Whether this counts as Bernoulli's Principle is apparently a matter of definition. In my book, flat wings work by deflecting the air down, but this link suggests that it's equivalent to the Bernoulli explanation.

Here is a question that clarifies why asking about Bernoulli's principle to the exclusion of other fluid-based lift generation makes no sense.

@romkyns - I would agree with that. And that would probably mean that the OPs question would pretty much be answered that EVERY flying machine operates on various aerodynamic properties, not just Bernoulli.

It would be good to define the term flying machines. For example, a regular bullet is not flying from the gun to the target, or is it?

@mins "machine" probably was too broad of a term. "Flying surface" would have been better. Though the original question was about "machines".
I would argue that a bullet is still exhibiting characteristics of "flight", though like a football or baseball, it's "flying" more because of an excess of "thrust". Even the shape of the bullet can determine its range, though that begins to get into the definition of "flying". :-)

@Shawn Except rockets in general; they deal with atmosphere,  but in general they rely solely on the rocket for lift. In particular, the Apollo LEM didn't rely on any atmospheric effects for anything :)

@Shawn: Good! I was thinking of excluding stuff which have a trajectory mainly because of their initial velocity (otherwise everything can be thrown and be claimed to fly). That would exclude spacecraft in orbit, but not rocket before engine cut-off.

@cpast - It would depend on where the rocket is. A rocket is an object with a way excess of thrust to its weight. If it's in a fluid (even air) then it would still exhibit characteristics of "flight" and be affected by Bernoulli. But that's getting way into the depths of the physics of "flight". Essentially, anything that moves fast enough will "fly" because of pretty much the same physics that allow an airplane wing to do it slower. And I would argue that anything operating in space is missing the critical ingredient for Bernoulli - fluid.

I believe Bernoulli's principal applies even in the case of a perfectly flat paper airplane wing, just as it applies to a symmetrical wing or even an inverted wing. Basically, angle of attack still causes the air to take a longer path over the upper surface of the wing. See http://hyperphysics.phy-astr.gsu.edu/hbase/fluids/airfoil.html

Space Shuttle on re-entry - flies like a brick :-)

@Russell McMahon - Good example of what I said. Space Shuttles were excellent gliders provided they were moving fast enough.  --- Nice. Mach 3 on re-entry and above Mach 1 until about 25 miles out from touchdown. It comes in on a 19 degree glide slope and touches down at 220 MPH. That's moving pretty quickly. Considering there's no go-around option, that's VERY impressive piloting. http://spaceflight.nasa.gov/shuttle/reference/basics/landing.html   Up until the "flare" that seems more Newton than Bernoulli. :-)

i see paper airplanes' "flight" having more to do with friction and slicing through the air than attributing bernoulli.  or is this part of the principle?  why do feathers "float" down to the ground when dropped?

@Shawn In fact, one NASA site talking about incorrect-but-popular lift explanations says that the Shuttle on re-entry is just about the one time the popular "action-reaction" theory of lift (in which lift is the physical deflection of air downwards when it hits the wing) gives accurate numbers (as density is very low and speed very high).

@erich A paper airplane when flying generates lift in much the same way as any airfoil, including the role of Bernoulli's principle. If you simply drop the paper airplane so that it falls perpendicularly to its wing surface, then only drag is holding it up. My recollection of what is written about this is it falls faster that way. Some dust particles hardly fall at all. A feather's fall is somewhere between these two phenomena.

@TylerDurden Three words "Angle of Attack".

How about all lighter-than-air vehicles:

Hot air balloons
Hydrogen- or helium-filled balloons
Airships

If you want to restrict the choice to heavier-than-air vehicles, rockets should still qualify.
You may also include VTOL aircraft which do not rely on their wings during hover, their internal turbo machinery would still use Bernoulli's principle, however, so for me they do not qualify.

Interestingly airships might not pass muster here. (It depends how pedantic you want to be : They float because of buoyancy, but the propellers that move them are airfoils, so if that directional control is part of "flight"…)

i wouldn't disqualify any answer for using bernoulli at all, but it's not responsible for the actual flight (controlled or uncontrolled).  like peter's vtol example - bernoulli might be responsible for acceleration of the airflow, but the thrust vectoring downward is what actually gets it off the ground.

I think if you're going to disqualify VTOL turbojets you should probably disqualify rockets as well - the turbomachinery of a liquid rocket uses Bernoulli's principle, and the nozzles of all rockets do as well.

Air balloons and rockets are two examples:

Air balloons fly by varying the density of the aircraft to lighter
than air.
Rockets fly by redirecting exhaust gas downward.

When the F-35 hovers, it too uses engine exhaust to counter the weight. However, their internal turbines still uses Bernoulli's principle to produce thrust.

It's a wonder there isn't a melted hole in the tarmac hovering at that height, what an extraordinary photo!

@PeterWone That happened at Oshkosh one year.  They actually blew a hole in the runway and it had to be shut down!

That flap on the back makes it look like the canopy is open. That was confusing...

There is the potential to melt/burn a hole in the tarmac, for the jet nozzle in the back.  For the nozzle in the front, there's no jet exhaust involved.  A shaft off the front of the engine spins a downward-directed turbine, which just moves air from above the plane to below the plane.  This is necessary because, if there was jet exhaust coming off the forward turbine, there's the potential that the intakes could ingest too much exhaust, with too little available oxygen, and flame out.  The large volume of unheated air from the forward turbine helps moderate the temperature hitting the tarmac.

Arguably rockets employ Bernoulli's principle in that the combustion chamber tapers towards the throat to accelerate the exhaust...

Airplanes :)
http://www.allstar.fiu.edu/aero/airflylvl3.htm
Although Bernoulli's principle is part of the reason why airplane wings generate lift, they also rely on displacing air downwards, in a similar way that the giant augur would, or in a similar way that a sail can convert a crosswind into forward momentum.

Else how would they fly inverted?

Although, actually, perhaps I spoke too soon.
http://www.grc.nasa.gov/WWW/k-12/airplane/wrong2.html
Seems like it's more complicated. Apologies!

Actually, when you're sailing from close-hauled to a beam reach the sail shapes to form an airfoil that is trimmed to produce laminar flow and "lift".  This is definitely bernoulli in action.

I read this page awhile ago and have been looking for a link to it. It's the best description of how wings work I've ever seen.

The sail of a sailboat is an airfoil on most points of sail (except when running nearly directly downwind, when the boat actually slows down because the sail is less effective then), but it is an airfoil with very nearly the same path distance along the high-pressure and low-pressure sides. Neither is there any obvious constriction of the airflow on the low-pressure side of the sail. Nevertheless, a low-pressure region is developed, which (by Bernoulli) tells us the air must be accelerated as it passes around the sail. The geometry of the airflow is more complicated than that of the sail.

If I understand Bernoulli's principle correctly, it's the interaction of solid surfaces with fluids that attach and flow along. In this regard Leonardo's craft would be using Bernoulli's principle. If it were not, the air wouldn't go down but towards the outside or "up" along the blade.
In fact first propellers looked quite like that design and were used on boats. They were derived from Archimedes' screws. Experiments showed that less "propeller" created less drag in the water, i.e. running more efficiently. Extrapolating that to the lesser viscosity of air led to even slimmer propeller blades.
So it's like the other answers pointed out, alternatives to Bernoulli's principle are:

displacement -> lighter than air
impuls -> rockets
electromagnetism -> transrapid (although it's altitude is in the order of centimeters)

Arguably there might be some sort of antigravitation possible employing the gyroscopic effect. But I never heard of anyone successfully doing that. However I remember seeing a Youtube video that I can't seem to find again. In it was a physics professor, who spun up a heavy weight on a long stick to 10.000 RPM and then lifting it single handedly at the end of the stick. Didn't seem to be much of an effort as long as he guided the stick into a spiral motion.
On the matter of planes using the Bernoulli principle, aircraft wings do displace air, but as they are heavier than the displaced air this does not create enough lift for an aircraft to fly. I think what @Nick means with "displacing downwards" is the same as what @erich means with "push the air below it down". The actio=reactio in this is termed impulse in physics. Yes, this also contributes some lift but is also neglectible as there isn't much (mass of) air pushed down. You can see that in wind channel tests of wing profiles or when aircrafts fly through smoke. The overwhelming majority of lift is in fact generated by the difference in pressure between the upper and lower side of the wing. This pressure difference is due to Bernoulli's principle. An aircraft flying inverted adjusts its angle of attack to compensate for the mismatch in wing profile. Actually only aircrafts designed to fly inverted can safely do so. Aerobatics have almost neutral wing shapes that create lift only according to angle of attack plus they have lots of excess power to generate lift from. For more on negative lift, angle of attack and flying inverted see the answer to this : If the profile of a wing pulls a plane up, why can planes fly inverted?

Good point regarding Maglevs. Microgravity will make it hard for scientific probes to move on small celestial bodies, and rotating masses are used which are stopped suddenly, letting the probe jump. But this is less flying than hopping.

To me "the interaction of solid surfaces with fluids that attach and flow along" sounds like a description of the Coandǎ effect. I think Bernoulli's principle, in its simplest form, is a relationship between total energy and pressure in an incompressible fluid flow. (I don't really know fluid dynamics, though, so this gloss may be inaccurate.)

Note, that the air is directed downwards and it is needed to generate (dynamic) lift due to principle of action and reaction. More of it is however pulled down from over the wing than pushed from under it unless the wing is stalled.

Only aircraft designed to fly inverted can safely do so, but it is not because the wings wouldn't be able to provide lift in the other direction. The main reasons are that normal fuel systems don't work inverted (the fuel port in the tank gets above the fuel level) and due to structural load limits (elements normally under compression-loaded become tension-loaded and vice versa and are not built for that load).

@Vectornaut: Yes, Bernoulli's principle is just expression of conservation of energy and is totally insufficient to explain lift. The pressure difference is due to conservation of energy, but first we need to know the flow velocity and direction and we need viscosity and inertia for that (the air flowing over upper and lower surface don't reach the trailing edge at the same time). Coandǎ effect is somewhat different though as it describes stream of fluid in a steady environment while lift is usually generated in uniform flow.

"Aircraft wings do displace air, but as they are heavier than the displaced air this does not create enough lift for an aircraft to fly." It's not mass of the air and the aircraft that need to be equal, but rather the forces that they apply to each other. These are, in fact, equal in magnitude (and, of course, opposite in direction.) Flying doesn't break Newton's Third Law (ignoring relativistic effects, at least.) The weight of the air being accelerated does not determine the amount of lift generated. The change in momentum of the air does, though (because it's directly related to force.)

"In it was a physics professor, who spun up a heavy weight on a long stick to 10.000 RPM and then lifting it single handedly at the end of the stick." Are you talking about this video? https://www.youtube.com/watch?v=GeyDf4ooPdo

…giant auger. This design would not have exploited Bernoulli's Principle…

Wings and propellers generate lift by exactly the same principle. The auger would work just like the slender rotating wings of a modern helicopter, just less efficiently.
Generally speaking, anything that flies flies because it generates some force that balances gravity. It can generate the force by using buoyancy or accelerating reaction mass.
Buoyancy is what balloons and airships use. It has great advantage that it does not need any energy. It has disadvantage that it needs huge structure, because air has very low density and thus provides only very little buoyancy.
The other option, moving reaction mass, can be again done in two ways: by expelling material carried for the purpose or by accelerating the surrounding air.
Expelling material carried for the purpose is what rockets do. It is the only currently working way to accelerate in space where outside reaction mass is not available, but for aircraft it is extremely impractical, because a lot of reaction mass is needed and lifting it needs more reaction mass and so on.
So what remains is accelerating surrounding air. And this always boils down to moving a slanted surface through it that always accelerates it using the same principle. Linearly moving wing, rotating wing/propeller, turbine or augur are all slanted surfaces moving through air.
The most important properties of air here are viscosity and inertia. Due to viscosity the flow tends to remain attached to the wing and due to inertia it continues downwards after flowing off the downward-slanted trailing edge.
Then you can use the simple argument of action and reaction—the air is accelerated downward, so the wing must apply force to it and therefore the air applies reaction force of the same magnitude and opposite direction to the wing, the lift—or you can use viscosity, inertia, conservation of mass and conservation of energy (that is Bernoulli's principle) to calculate how the pressure field around the wing looks and notice the lower pressure above the wing then under it.
Neither explanation is more correct than the other; laws of nature all hold at the same time and there are multiple ways to calculate most things. However, Bernoulli's principle is not itself sufficient to explain lift. It is only one of several important properties of fluids that together explain it.

i think of a simple household oscillating fan.  how much is bernoulli involved in the rotation of the angled blades pushing air?  i would think very little.

on the other hand, in putting your hand behind the fan, very little acceleration of air on the back side of the fan can be detected (compared to the front).  is the increased airflow coming off the front of the fan an effect of a resultant higher pressure (a la bernoulli)?

@erich: The principle is still the same—the air flows along the slanted blades and gets accelerated and reduced pressure above the blades is what transfers the energy.

@erich: The acceleration upstream of the fan is lower, because the air is drawn from all directions. That is the case with any kind of propeller.

Planes (physics.stackexchange.com)

Basically planes fly because they push enough air downwards and receive an upwards lift thanks to Newton's third law.

And Bernoulli effect is the consequence, not the cause. Or:

Air is still (speed 0). Then a wing arrives. Air over the wing says
"Oh, I was stopped, but now I'm over the wing. So, let's accelerate to
back, hence low pressure is created for pulling the wing up." This is
absurd.

What makes the air move faster to rear above the wing? Itself? No, a lower pressure. Thus, cause: lower pressure. Effect: air moves.
And what does it cause the lower pressure? Not its effect (air moving), of course.
Now, there is only one suspect left: deflection of air.
In sum:
Wing deflects air (downwash) => this causes simultaneously lift and pressure changes (lower pressure above the wing). Lower pressure over the wing causes the higher speed of air on that side.
Also note
It is worth to mention that the Bernoulli equation is valid to calculate the amount of lift. Here we are estimating lift not by measuring the downwash itself, but by measuring a direct consequence of it: pressure changes.

Your text says [physics.se], but the link is to [aviation.se], is that in error? Also, I'm not sure I'm following your logic, you might want to add a bit more detail instead of using terse, incomplete sentences.

@FreeMan Sorry the link and cite is to physics. Now it's right.

No. "Flying" has come to refer to the non-intuitive or 'magical' mechanisms of travel through air - and that 'miracle of flight' is Bernoulli at work.
Rockets and balloons can only go straight up, they cannot fly (ie. travel horizontally). Well I suppose jet packs count. I do not think we should call that flying. "Jetting" maybe ...
We could categorise ways of getting about in air as:

Flying. Bernoulli pressure differential devices (including propellors).
Scooping. Things which mechanically displace the air to support or propel them -  paddles/scoops/augers/blades/flat wings (are there any working examples which do not also use Bernoulli? Maybe insects? Did anyone work out yet how bees fly?)
Positive Impulse. Things which create new air [or gas] to support or propel them - Rockets, steam jets, photon rockets
Negative Impulse. Things which destroy air in front to support or propel them - not sure if anyone has made a supercooler negative impulse engine but I presume it works in theory (it would have to squirt out liquid air which would be type 2 thrust as it expanded ..)
Anti gravity devices. Would move sideways by interacting with planets.
Magnetic levitation - close range only.
Floating. Balloons do not really count as flying though because they cannot move sideways without using other principles.
Riding. Wind (kites,leaves) , convection currents (house dust) or thermals (gliding, clouds).
Jumping ( or getting from a to b quick before gravity kicks in ). I think in this category we also have electromagnetic radiation - which does a good job of 'flying' long distances very quickly and has been around a long time.

So 'No' is probably the answer.


text:
Why not separate out the two definitions of V-1 into two separate Vspeeds?
V1, officially the takeoff decision speed, has, somewhat infamously, two separate definitions:

It is defined as the minimum speed at which, if one engine fails, the pilots can press to liftoff and still maintain safe obstacle clearance during climbout.
It is also defined as the maximum speed at which a rejected takeoff can be initiated and the aircraft safely stopped on the runway without the use of reverse thrust.1

These two speeds are only the same if the aircraft is operating at the absolute maximum allowable weight for that particular takeoff; if the aircraft is lighter than the maximum allowable takeoff weight,2 the first speed (the minimum “go” speed) is slower than the second speed (the maximum “stop” speed),3 forming a range of possible V1s, and the pilot(s) get to choose whatever V1 they want from within this range.
Instead, why not separate out the two definitions into two separate Vspeeds; for instance:

V0: The minimum speed during takeoff at which, in the event of the sudden failure of a single engine, the takeoff can be continued and safe obstacle clearance guaranteed during climbout.
V1: The maximum speed during takeoff at which a rejected takeoff can be initiated and the aircraft brought to a stop on the paved surface of the runway without the use of reverse thrust.

With the current system, there is a variable length of time before V1 during which it is already possible to safely continue following a minor to moderate failure rather than attempting a risky near-V1 RTO, and/or a variable length of time after V1 during which it is still possible to reject without overrunning should a serious failure occur, but neither the minimum “go” speed nor the maximum “stop” speed is ever called (unless the pilots happened to select one of those specific speeds as the V1 for this particular takeoff), thus potentially forcing the pilots to reject when it would be safer to continue, or to continue when it would be safer to reject.
In contrast, if the minimum “go” speed (“V0”) and the maximum “stop” speed (“new V1”) are both called, and called separately, then the pilots would know for sure both when it first becomes possible to safely continue the takeoff, and, also, when it stops being possible to reject the takeoff without overrunning the runway.  This would allow the takeoff to be separated into three distinct phases, rather than two:

Speed < V0: Abort for any failure.
V0 ≤ speed ≤ new V1: Continue for minor to moderate failures (such as tyre failures without fire, or birdstrike without attendant engine or flight-control damage); abort for more serious failures (such as engine failures, tyre failures with fire, or partial hydraulic failures).
New V1 < speed: Continue for any failure that does not render the aircraft unflyable; abort only for catastrophic failures that preclude liftoff and/or safe, controlled flight (such as a flight-control failure [prevents aircraft from lifting off and/or renders aircraft uncontrollable once airborne], multiple simultaneous engine failures [degrades aircraft acceleration so severely as to preclude liftoff], total landing-gear collapse [massively increases runway drag, likely severely enough to preclude liftoff, and carries high probability of causing severe structural damage], or pitot-static failure [robs pilots of altitude and airspeed information, making controlled flight impossible]).

So why aren’t the minimum “go” speed and the maximum “stop” speed split into two distinct speeds, called out separately during takeoff?

1: For this reason, V1 is generally taken as the speed beyond which one should not attempt to reject a takeoff if the aircraft is still flyable.
2: The maximum weight at which the aircraft can take off from that runway with that performance under those atmospheric conditions and still be assured, throughout the takeoff, of the ability, in the event of a single engine failure, to reject the takeoff without overrunning the runway, to continue the takeoff without striking or coming dangerously close to objects off the end of the runway, or both.  Not to be confused with the maximum takeoff weight, which is the absolute maximum weight at which the aircraft, assuming a perfectly dry, 0C atmosphere and a frictionless runway of infinite length, is physically capable of lifting off and maintaining flight should one engine fail.
3: If the aircraft were heavier than the maximum allowable takeoff weight, there would be a section of the takeoff during which, in the event of a single engine failure, the aircraft would be incapable of continuing the takeoff and maintaining obstacle clearance, yet already moving too fast to stop on the remaining runway - in short, neither a safe continued takeoff nor a safe rejected takeoff would be possible.  Which is why a) that weight is the maximum allowable takeoff weight, and b) it’s illegal to knowingly take off overweight.


text:
How are the dry lake runways at Edwards AFB marked, and how are they maintained?
In addition to its paved runways, Edwards AFB in California has several runways on the bed of Rogers Dry Lake, famously used in the past for (among other things) Space Shuttle landings. Satellite imagery shows these runways marked with a very high-contrast black-looking material. One can also spot vehicle tracks around the markings. There are also other interesting markings on the dry lake bed using what looks like the same material, such as a distance scale and a compass rose.

What material or method is used to make these markings? How are the markings maintained, as I imagine natural weathering would quickly cover up such markings?

A gigantic Sharpie™! (honestly, the first thing that popped into my head when I looked at that writing.)

They use oil, specifically SSH1 which is environmentally friendly. This oil replaces the tar that used to be used.

Source: Rebecca Amber, Can you see me now? Lakebeds 'restriped', Edwards Air Force Base, July 14, 2015.

Product sheet: http://staging.themartincompanies.com/wp-content/uploads/2016/11/SS-1h-07-25-16.pdf

Jim, is it SSH1 as Edwards' communications people state or is it SS-1h (slow setting emulsion #1, hard) as the manufacturer's own product sheet says? My money is on the manufacturer . . . .

The oil is sprayed on by tankers

Sourced from: https://www.edwards.af.mil/News/Photos/igphoto/2001259081/


text:
What is that invisible bump in the air called that occurs after completing a 360 degree turn?
Does that bump you feel after completing a level 360 degree turn in an airplane have a proper name? I've heard it called an "attaboy bump", but obviously thats not a proper name.
My understanding is that the bump occurs when a properly executed level 360 turn overlaps the disturbed air caused by the same aircraft's flight path into the turn.

Loss of separation with the next aircraft in approach?

It's your aircraft's wake, as in wake turbulence.

Yes. I think I worded my question wrong, but do you know if there is a name for intersecting your own aircraft's wake upon completion of a 360 degree turn?

@Devil07 I've never heard a special name for it, everyone I know just says "I hit my own wake"

me too, I was wondering if it had a special name. I say we hereby name it the "attaboy bump", unless you can think of a more appropriate one. ;)

Well, I had it flip me over once, so it was an oh s*@t bump then.

@GdD what kind of aircraft were you in?

It was a Cessna 172, I was practicing steep turns @Devil07

Wow, 8 words, 18 votes. That looks like a record which will hold a long time :-)


text:
Should I inform ATC about minor deviations to maintain VFR while on practice instrument approaches?
When talking to approach control for the purpose of performing practice instrument approaches in VMC with a safety pilot, the pilot (and safety pilot) is required to "maintain VFR." However, the pilot is also required to follow the controller's instructions and vectors.
When maintaining cloud clearances in order to comply with the "maintain VFR" requirement, it is sometimes necessary to maneuver around, under, etc. small clouds. Sometimes the maneuvering involves a lot of small corrections: maybe a few thousand feet off course, or going under a cloud by 500 to 1000 feet.
Do controllers expect to be told every time a VFR aircraft in VMC has to maneuver around small clouds? What phraseology is required? For example, is "maneuvering to maintain VFR" sufficient, or do you have to state each turn descent/climb etc.? At busy approaches it seems like a huge annoyance to controllers to call with every little course correction/adjustment to maintain VFR, but perhaps that is what they expect.

Yes, definitely. Approach is expecting you to fly the approach as published and/or instructed and if you can't do that for any reason then you need to tell them. They may be providing separation between you and other aircraft, and if you start maneuvering without any explanation that could make things difficult for them.
The last time it happened to me I was being vectored when my safety pilot told me that another aircraft was heading towards us. I turned and climbed and then told ATC "maneuvering for traffic, will resume 3000 and heading 150 when able". The controller acknowledged, waited until I was (more or less) back on course and then gave me another vector.
Having said all that, if you can't fly the approach without deviating all over the sky then you should consider if it's really worth it. First, because it may not be very useful or realistic practice, and second because if you put a higher workload on ATC then they may just drop you completely. The ATC orders 4-8-11 say:

[...] ensure that neither VFR nor IFR practice approaches disrupt the flow
  of other arriving and departing IFR or VFR aircraft. Authorize,
  withdraw authorization, or refuse to authorize practice approaches as
  traffic conditions require.

You make such a good point about it not being realistic practice if I'm having to maneuver repeatedly! Where I fly there tends to be small puffy clouds scattered in precisely the most inconvenient locations at around 1000 AGL. I've heard of sometimes safety pilot or even a CFI taking someone under the hood through these little cotton ball clouds. The pilot under the hood doesn't see them coming, but you can tell when you go through one, its about 1 or 2 seconds, but its still technically violation of cloud distances requirement.

If you are on a radar vectors clearance and you alter heading to maintain cloud separation for any length of time, the controller is going to notice it at some point and ask you what is going on, which would be more distracting than calling in your heading change in the first place, so you should declare heading changes to stay clear of cloud.  I would call in "XXX altering heading left to xxx degrees for cloud separation".  Not sure I'd climb or descend unless I absolutely had to because I think that can cause more grief for ATC, separation wise, than heading changes.

If there are enough clouds that maintaining VFR is non-trivial, then it's probably best to find another time/place to practice. If it's an everyday phenomenon in your area, though, talk to some local CFIIs for advice. You might even phone/visit the local ATC unit and see what they say; there may be special local rules to address it if it's that bad.


text:
Is a forward slip considered a "normal maneuver" under 91.175(c)(1)?
After an instrument approach in IMC, 91.175(c)(1) requires, among other things, that operations below the DH or MDA must allow for a "normal rate of descent using normal maneuvers."
Can someone point me to a regulation or a definition of what is a normal rate of descent and normal maneuvers under this regulation?
Specifically, my question is whether a forward slip is considered a normal maneuver for purposes of 91.175(c)(1)?

I think all you really have to go on is the FAA's "unusual attitude" definition:
<Pitch attitude greater than 25°, nose up.  Pitch attitude greater than 10°, nose down. Bank angle greater than 45°.   Within the above parameters, but flying at airspeeds
inappropriate for the conditions>. A forward slip that stays within those parameters would meet that requirement I would say, depending on how aggressive it is. For descent rates, what is "normal" depends on your appr speed, but generally, descent rates over 1000 fpm are considered excessive.  I don't think you will find any go-no-go limits.

@JohnK agreed, to me a forward slip is as normal as using flaps. However, I'm looking for some legal documented backup as it pertains to 91.175(c)(1). I think that definition you described is related to the "upset" AC on UPRT. Probably a good place to start though.

Perhaps it would help if you explained the motivation behind the question.

@JuanJimenez the motivation is curiosity, but let me give you a scenario. If someone from your local FSDO was watching you pop out from the clouds on an instrument approach and you performed a forward slip to land, would it be a violation of 91.175(c)(1), because a forward slip is not a "normal" maneuver?

Its not an easy question. I've spend some time researching it, but thats why I posted it here. I'm going to keep researching it and if I find a definitive legal answer I'll post it. I might have to dig into FAA advisory opinions.

You popped out of the clouds, found yourself high and executed a forward slip to safely land? Aside from the fact that I would find it ridiculous for anyone from the local FSDO to get riled up about that, the rule is not applicable in your example. If you are too high, by definition you have a visual on the runway. DH no longer applies, as it is the altitude above the rwy threshold at which you must initiate a missed approach if you do NOT have a visual reference to continue the approach.

I can't find any specific definition of "normal maneuvers", probably because it varies a lot by aircraft type and situation. But I did find AC 120-29A - Criteria for Approval of Category I and Category II Weather Minima for Approach that gives some indication of what the FAA considers not normal (section 4.3.1.6):

Part 91, section 91.175 requires that approach procedures should be
based on use of “normal maneuvers” before and after passing DA(H) or
MDA(H). Normal maneuvers typically do not involve use of bank angles
greater than 30 degrees, pitch attitudes in excess of 25 degrees nose
up or 10 degrees nose down, or sink rates in excess of 1100 ft. per
minute below 500 ft. HAT while maneuvering to land within the
touchdown zone, during go-around, or during a rejected landing. During
a missed approach, pitch attitudes in excess of +30 degrees or bank
angles greater than 30 degrees would typically be considered
excessive.

But even if there is a specific definition of normal maneuvers out there somewhere, I think the context is important too. 91.175 is about instrument approaches, not general flying. So I think you have to ask if slipping to land is a normal maneuver during an instrument approach and I'd say no.
The entire point of an instrument approach is to get you to the runway safely and predictably, and there's a lot of emphasis on stable approaches. I can't think of any obvious reason why you'd need a forward slip if you've flown an approach successfully. You might be able to come up with some scenarios (circling to land? shooting an approach with an MDA of more than 2000' AGL?) however I'm not convinced that it's a normal technique in the specific context of instrument approaches.
If you look at what the FAA says about forward slips in the Airplane Flying Handbook Chapter 8 it strongly suggests that slips are for limited and unusual situations:

Intentional slips are especially useful in forced landings and in
situations where obstacles must be cleared during approaches to
confined areas. A slip can also be used as an emergency means of
rapidly reducing airspeed in situations where wing flaps are
inoperative or not installed.

I find it hard to see how those examples fit with executing an instrument approach. But that's just my opinion. If you happen to know a DPE it would be a great question to ask them.


text:
Who has the responsibility to make altimeter corrections in cold temperatures?
I work as air traffic controller in Asia and we refer to both ICAO and FAA regulations. As winter is coming, there is a debate on altitude correction (or altimeter correction?) for cold temperatures. Some insist that we (ATC) don't have the responsibility to make altitude correction, and the others insist that we have, when ATC performs radar vectoring. (We know that the pilots have responsibility when IAP.)
In related to this, ICAO DOC 8168 states (Vol 1, Chap 4 Altimeter correction):

The pilot is responsible for these corrections, except when under radar vectoring. In that case, the radar controller issues clearances such that the prescribed obstacle clearance will exist at all times, taking the cold temperature correction into account.

So, I've tried to find references about this but failed.
Here're my questions.
1) Is there a document or manual for ATC about how to make altitude corrections when radar vectoring?
2) Why is there no altitude correction for hot temperatures that make for a steep angle of descent?
3) Should ATC-issued altitudes take into account temperature-induced altimeter error, or does should ATC issue the true altitude and leave the responsibility on the pilot for making the correction?

Hot temps aren’t really a problem since the plane will be flying at an altitude above what his altimeter reads. With low temps it can be below the reading risking terrain contact. I’m not sure what you’re asking in point 3. What barometer has an error?

Shouldn't you be asking you management this, rather than getting advice from random strangers on the internet? As someone who sometimes flies in planes I hope that you controllers can work out what the correct process is without our help.

I don't have enough points to make a comment so I'll just leave this one...
http://code7700.com/altimeter_temperature_correction.htm
All throughout, it's
Pilot In Command...
Pilot In Command...
Pilot In Command...
Pilot In Command...

4.1.4 Air traffic control (ATC). If an aircraft is cleared by ATC to an altitude which the pilot-in-command finds unacceptable due to low temperature, then the pilot-in-command should request a higher altitude. If such a request is not received, ATC will consider that the clearance has been accepted and will be complied with. See Annex 2 and the PANS-ATM (Doc 4444), Chapter 6.

I post couple of things i found. Basically this:
According to ICAO PANS OPS, minimum vectoring altitudes shall be corrected for temperature. The temperature correction shall be based on seasonal or annual minimum temperature records. In turn, ATC authorities are required, as per ICAO PANS ATM, 8.6.5.2, Note 2, “to provide the controller with minimum altitudes corrected for temperature effect”.
ICAO Doc 8168 - Aircraft Operations - Vol I, Part III, §1, Ch. 4] Note.— This chapter deals with altimeter corrections for pressure, temperature and, where appropriate, wind and terrain effects. The pilot is responsible for these corrections, except when under radar vectoring. In that case, the radar controller issues clearances such that the prescribed obstacle clearance will exist at all times, taking the cold temperature correction into account.


text:
What was the yearly number of MiG-15's produced?
Wikipedia's article on the MiG-15 only states a basic number of 12,000 produced natively, with up to 6,000 more produced in other countries. But it does not list any years for this.
When did mass-production start and end for the MiG-15 in the Soviet Union? This would at least let us divide 12,000 by the total years to get an average production rate. Ideally I'm looking for the number built each year, as this will surely vary year to year.

You have your numbers now :)

There is hardly anything that can't be found with the help of a few friends and the Library of Congress. "Истребитель МИГ-15 (MiG-15 Fighter)" ISBN 9785857290194 Pp.52-57.
Plant No.1 (Kuibyshev):
             MiG-15    MiG-15bis    MiG-15Pbis     UTI MiG-15bis
1949 Plan    550
     Actual  510
1950 Plan    300       350                          50
     Actual  301       401                          50
1951 Plan              792         5               365
     Actual            820         5               371
1952 Plan              425                         315
     Actual            460                         333
1953 Plan
     Actual    2                                   127

Non-flyable [what the heck is that??] MiG-15: 2 in 1949, 4 in 1950.
10 knock-down UTI MiG-15 kits were produced in 1951.
Plant No. 153 - Novosibirsk
             MiG-15    MiG-15bis    MiG-15Pbis     UTI MiG-15bis
1949 Plan    550
     Actual  144
1950 Plan    300        500
     Actual  308        360
1951 Plan              1173
     Actual    1       1196
1952 Plan               840
     Actual             863
1953 Plan                                          200
     Actual               1                        209
1954 Plan                                          700
     Actual                                        715

Plant No.381 (Leningrad): 1949 - 75 MiG-15
Plant No.21 (Gor'ky):
             MiG-15bis (type 53)    MiG-15Rbis (type 55)
1950 Plan    350
     Actual  367
1951 Plan    937                     60
     Actual  992                     64
1952 Plan    395                    300
     Actual  425                    300

Plant No.31 - Tbilisi
             MiG-15bis (art. 50)
1951 Plan     30
     Actual   35
1952 Plan    190
     Actual  190

Plant No.126 - Komsomo'ls'k-NA-Amure
             MiG-15                 MiG-15bis
1950 Plan                           250
     Actual    1                     42
1951 Plan                           337
     Actual                         362
1952 Plan                           400
     Actual                         428

Plant No.292 - Saratov
             MiG-15    MiG-15bis    MiG-15Sbis
1950 Plan              275
     Actual    8?      131
1951 Plan              457          100
     Actual            509           49
1952 Plan              350
     Actual            354

Plant No.135 - Kharkiv
                UTI MiG-15
1950 Plan              25
     Actual             6
1951 Plan              50
     Actual            50
1952 Plan             150
     Actual            85
1953 Plan             150
     Actual           158
1954 Plan             200
     Actual           212

Plant No.99 (Ulan-Ude)
                UTI MiG-15
1951 Plan              75
     Actual            29
1952 Plan             125
     Actual            53
1953 Plan             150
     Actual           127
1954 Plan             200
     Actual           206
1955 Plan             225
     Actual           245
1956 Plan
     Actual           173
1957 Plan
     Actual           113
1958 Plan
     Actual           106
1959 Plan
     Actual            65

Totals for the USSR (may contain errors, haven't double-checked):
|      | Combat MiG-15 and variants |  UTI MiG-15   |
| Year | Plan          | Actual     | Plan | Actual |
| 1949 | 1175          |  729       |    0 |    0   |
| 1950 | 2325          | 1911       |   75 |   56   |
| 1951 | 3891          | 4033       |  490 |  450   |
| 1952 | 2900          | 3020       |  590 |  471   |
| 1953 |    0          |    3       |  500 |  621   |
| 1954 |               |            | 1100 | 1133   |
| 1955 |               |            |  225 |  245   |
| 1956 |               |            |    0 |  173   |
| 1957 |               |            |    0 |  113   |
| 1958 |               |            |    0 |  106   |
| 1959 |               |            |    0 |   65   |

Non-flyable versions may be just the full scale models for final wind tunnel testing. +1 and it better incur more +1's because it's not every day an answer comes along with itemized data in a table.

Yup, very nice answer!! Including the name of the tome in addition to its ISBN would be the coup de grâce!

@FreeMan it's a Russian book whose translation is Fighter MiG-15. Sadly I could not find it in Google Books or something else that lets you read it online.

Excellent, @schwern! (Not that I can read Russian...)

Could a non-flyable unit also be for flight- or maintenance-crew familiarization purposes?

@RussellBorogove - dunno, six planes are somewhat too few for the whole SovAF. I've been offered some guesses: they were destined to go a) to other plants, or b) to major fighter schools. I'm also intrigued by the knock-down kits.

@DeerHunter the kits might have been for supply to some foreign nation, to be shipped by sea rather than flown over.

My reference is the Osprey Encycopledia of Russian Aircraft, but even here no yearly figures are listed. But it gives a little more details.
The MiG OKB started work on type S (for strelovidnost = swept) in March of 1946 and based it on German work which had determined that a backward-swept midwing configuration with central intake was the best compromise. The first prototype S-01 flew first on Dec. 30, 1947, followed by S-02 on May 27, 1948. The third prototype S-03 had numerous changes applied (many of them diligently listed in the book) and flew first on June 17, 1948. In August 1948 it was selected for mass production as the MiG-15. Initial production started at GAZ-1 with the first aircraft delivered to service units on October 8, 1948. The Politburo decided on March 20, 1949, to increase production, so the plants that were building the La-15, Li-2, Yak-17 and -23 were all switched over to the MiG-15. Until 1956 12,000 units were built in 17 versions, more than half of them (6,500) as two-seater trainers (MiG-15UTI), built from the second half of 1950 on.
The Czech license-built S-102 are given with 853 units, built between 1953 and 1955 and the Polish LIM-1 with 54 units.
The MiG-15bis is listed separately and started production from early 1952 on. In Czechoslovakia 620 were license-built as the S-103 and in Poland as LIM-2 (no numbers given).
The book is clearly more for engineers than for production people. Would you know that the MiG-15 ejection seat needed different cartridges in winter than in summer, or that the MiG-15 Burlak was equipped with a harpoon to catch a cable towed behind the wing of a bomber, so it could fly in tow to be available as fighter cover over the target area? Since the engine was shut down for cruise, the pilot froze abjectly.
The MiG-17 started deliveries from October 1952 on, so it is fair to assume that the bulk of MiG-15 were built between the second half of 1949 and 1952. If you split those three years evenly, the yearly production figure would be 4,000. Now subtract a few hundred for the initial production and some more for the later production years (mostly MiG-15UTI), and I would expect that the highest yearly production was maybe 3,000, with many of the 6,500 MiG-15UTI built between 1953 and 1956.
With the production numbers listed in the book I have a hard time to reach anything close to those 18,000 given in Wikipedia. Many of the MiG-15s flown in East Bloc countries were produced in Russia and exported. The number of exported MiG-15UTI is given as over 1,960 alone.

IIRC, Poland was given license to produce the MiG-15 and built approximately 6,000 of them. +1 for your reference and stats and the interesting factoids, although the bomber-towed MiG was just an experiment to see if carrier aircraft could "extend the range", so to speak, of small maneuverable fighters. 12,000 in 3 years is a good enough estimate for my purposes.

@DrZ214: The 12,000 include the UTI version which was in production until 1956. I would expect that in the main years maybe 10,000 were produced. No word in the book about the 6000 Polish MiGs, though - all Polish variants are listed without numbers. You are right about the Burlak, and there were many more experiments like sviveling guns (which produced an unacceptable pitch-down when fired into the circle in trials).

Never heard of the swiveling gun before. Was that in a spherical nose mount so at least it could be aerodynamic? If so, how would it reload ammo?

This article from 1952 states an annual production of 5,500 to 6,200 aircraft. Even if this represented the peak production, that seems a bit high compared to the total production number of over 18,000. Some details of how these sorts of estimates were made is available in this document.

I would be very cautious with putting any particular weight on this number - as was later discovered during the "bomber gap" debates, Western analysis of Soviet aircraft production in the period, and especially publicly reported figures, was wildly inaccurate.

Peak production was 4483 aircraft in 1951 (and 10 knock-down kits).

The PZL Mieliec states it build
237 pieces of Lim-1 [inc. 1A & SB] (from '52 to '54) and
510 pieces of Lim-2 [inc. 2A & SB] (from '54 to '56)
Other sources state that less then 220 Lim-1 and less then 500 of the Lim-2 has been build
The Aero Vodochody build
850 pieces of S-102
620 pieces of S-103
and over 4200 pieces of the CS-102

could you provide a link to these sources?

PZL Mielec   http://www.polot.net/wsk_mielec_lim_1_mig_15/zestawienie    http://www.polot.net/wsk_mielec_lim_1_mig_15/historia    http://tmzm.mielec.pl/archiwum/m2HP_L_Limy.htm